Chemistry_Grade_10-12 (1).pdf

Look at iron and steel for example iron loses its

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others. Look at iron and steel for example. Iron loses its magnetism quite quickly if it is taken away from the magnet. Steel on the other hand will stay magnetic for a longer time. Steel is often used to make permanent magnets that can be used for a variety of purposes. Magnets are used to sort the metals in a scrap yard, in compasses to find direction, in the mag- netic strips of video tapes and ATM cards where information must be stored, in computers and TV’s, as well as in generators and electric motors. Activity :: Investigation : Magnetism You can test whether an object is magnetic or not by holding another magnet close to it. If the object is attracted to the magnet, then it too is magnetic. Find some objects in your classroom or your home and test whether they are magnetic or not. Then complete the table below: Object Magnetic or non- magnetic Activity :: Group Discussion : Properties of materials In groups of 4-5, discuss how our knowledge of the properties of materials has allowed society to: develop advanced computer technology provide homes with electricity find ways to conserve energy 1.8 Summary All the objects and substances that we see in the world are made of matter . This matter can be classified according to whether it is a mixture or a pure substance . A mixture is a combination of one or more substances that are not chemically bonded to each other. Examples of mixtures are air (a mixture of different gases) and blood (a mixture of cells, platelets and plasma). The main characteristics of mixtures are that the substances that make them up are not in a fixed ratio, they keep their individual properties and they can be separated from each other using mechanical means. 18
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CHAPTER 1. CLASSIFICATION OF MATTER - GRADE 10 1.8 A heterogeneous mixture is non-uniform and the different parts of the mixture can be seen. An example would be a mixture of sand and salt. A homogeneous mixture is uniform, and the different components of the mixture can’t be seen. An example would be a salt solution. A salt solution is a mixture of salt and water. The salt dissolves in the water, meaning that you can’t see the individual salt particles. They are interspersed between the water molecules. Another example is a metal alloy such as steel. Mixtures can be separated using a number of methods such as filtration, heating, evapo- ration, centrifugation and dialysis. Pure substances can be further divided into elements and compounds . An element is a substance that can’t be broken down into simpler substances through chemical means. All the elements are recorded in the Periodic Table of the Elements . Each element has its own chemical symbol. Examples are iron (Fe), sulfur (S), calcium (Ca), magnesium (Mg) and fluorine (F).
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